A microgrid includes a plurality of distributed energy resources such as controllable distributed electric generators and electrical energy storage devices. A method of controlling operation of the microgrid includes periodically updating a distributed energy resource schedule for the microgrid that includes on/off status of the controllable distributed electric generators and charging/discharging status and rate of the electrical energy storage devices and which satisfies a first control objective for a defined time window, based at least in part on a renewable energy generation and load forecast for the microgrid. The method further includes periodically determining power set points for the controllable distributed energy resources which satisfy a second control objective for a present time interval within the defined time window, the second control objective being a function of at least the distributed energy resource schedule for the microgrid.
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1. A method of controlling operation of a microgrid which comprises a plurality of distributed energy resources including controllable distributed electric generators and electrical energy storage devices, the method comprising: periodically updating a distributed energy resource schedule for the microgrid that includes on/off status of the controllable distributed electric generators and charging/discharging status and rate of the electrical energy storage devices and which satisfies a first control objective for a defined time window, based at least in part on a renewable energy generation and load forecast for the microgrid; periodically determining power set points for the controllable distributed electric generators which satisfy a second control objective for a present time interval within the defined time window, the second control objective being a function of at least the distributed energy resource schedule for the microgrid; periodically updating the distributed energy resource schedule and shifting the defined time window each time-the distributed energy resource schedule is updated, wherein the power set points for the controllable distributed electric generators are determined for at least two successive time intervals within the defined time window before the distributed energy resource schedule is updated again and the defined time window is shifted, wherein: the first control objective ensures a total power generation capacity of all of the controllable distributed electric generators having an on status as indicated by the distributed energy resource schedule is greater than a critical load of the microgrid for the defined time window; and the first control objective is also a function of a correction factor that accounts for at least one of the controllable distributed electric generators having an on status being out of service during the defined time window so that the total power generation capacity remains greater than the critical load of the microgrid over the defined time window even if the microgrid is disconnected from a main grid or at least one of the controllable distributed electric generators is out of service in an island mode.
A method for managing a microgrid with distributed energy resources (generators, batteries) involves two periodic processes: 1) Updating a resource schedule based on renewable energy and load forecasts. This schedule sets generator on/off states and battery charge/discharge rates to meet a "first control objective" over a time window. This objective ensures enough power generation capacity exceeds critical load, even with generators offline or the microgrid disconnected. A correction factor accounts for potential generator outages or disconnection from power grids. 2) Determining generator power set points to meet a "second control objective" for the current time interval, considering the resource schedule. Power set points are determined for at least two time intervals before the schedule is updated. The resource schedule and time window are periodically updated.
2. The method of claim 1 , wherein the first control objective is also a function of an energy storage cost associated with the electrical energy storage devices.
The method of controlling a microgrid's operation also factors in energy storage costs when updating the resource schedule. The schedule includes on/off status of generators and charging/discharging status/rate of batteries, aiming for a "first control objective" which considers renewable energy and load forecasts. This objective ensures generation capacity exceeds critical load, even with generator outages or disconnection. The energy storage cost is now a component of the first control objective.
3. The method of claim 2 , wherein the first control objective limits the amount of charging/discharging permitted for the electrical energy storage devices over the defined time window so that the energy storage cost is minimized for the defined time window.
The method of controlling a microgrid's operation further refines the energy storage aspect. The "first control objective," which considers energy storage cost, limits the charging/discharging of batteries over the defined time window to minimize the energy storage cost during that period. The resource schedule dictates generator on/off states and battery charge/discharge rates. The objective ensures generation capacity exceeds critical load, even with outages or grid disconnection, while minimizing energy storage costs through charging/discharging limits.
4. The method of claim 1 , wherein the microgrid is configured to be connected to power grids in a grid-connected mode and isolated from all power grids in the island mode, and wherein the defined time window is shorter for the island mode than for the grid-connected mode.
The microgrid control method adapts to different operational modes. When connected to external power grids, the time window for the resource schedule (generator on/off, battery charge/discharge) is longer. When isolated (island mode), the time window is shorter. The resource schedule is based on renewable forecasts and load. The "first control objective" ensures adequate generation capacity, accounting for potential outages and disconnection, with shorter windows in island mode.
5. The method of claim 1 , further comprising: updating the distributed energy resource schedule each time the renewable energy generation and load forecast is revised.
The microgrid control method dynamically adjusts to changing conditions. The resource schedule (generator on/off, battery charge/discharge), initially based on renewable energy and load forecasts, is updated whenever those forecasts are revised. The "first control objective" ensures adequate generation capacity, even with outages or grid disconnection. This ensures the microgrid adapts to real-time forecast changes.
6. The method of claim 1 , wherein the distributed energy resource schedule is updated every hour or less frequently, and wherein the power set points for the controllable distributed electric generators are determined every fifteen minutes or more frequently.
The microgrid control method operates at different frequencies. The resource schedule (generator on/off, battery charge/discharge) is updated hourly or less often. The generator power set points, however, are determined every fifteen minutes or more frequently. The "first control objective" ensures adequate generation capacity, even with outages or grid disconnection. This two-tiered approach balances schedule stability with responsiveness.
7. The method of claim 1 , wherein the second control objective minimizes an operation cost of the microgrid for the present time interval while minimizing the extent by which the actual charging/discharging rate of the electrical energy storage devices deviates from the charging/discharging rate identified for the electrical energy storage devices in the distributed energy resource schedule.
The microgrid control method optimizes operational costs. The "second control objective," used to determine generator power set points, minimizes the microgrid's operating cost for the current time interval. It also minimizes deviations between the actual battery charge/discharge rate and the rate specified in the resource schedule. The "first control objective" is used for the resource schedule, ensuring adequate generation capacity.
8. The method of claim 1 , wherein the second control objective is also a function of line current and node voltage constraints imposed on the microgrid.
The microgrid control method considers grid constraints. The "second control objective," used to determine generator power set points, factors in line current and node voltage constraints imposed on the microgrid. This prevents overloading and voltage instability. The resource schedule is generated using the "first control objective" and is based on renewable generation and load forecasts.
9. The method of claim 1 , wherein the second control objective is also a function of a weighting factor applied to the charging/discharging rate identified for the electrical energy storage devices in the distributed energy resource schedule.
The microgrid control method allows for prioritization of battery usage. The "second control objective," used to determine generator power set points, incorporates a weighting factor applied to the battery charge/discharge rate specified in the resource schedule. This allows the system to prioritize or de-prioritize battery usage based on specific needs or conditions. The resource schedule is generated using the "first control objective" and is based on renewable generation and load forecasts.
10. The method of claim 1 , wherein the second control objective is also a function of a load shedding variable which accounts for planned outages in the microgrid so that load shedding is minimized over the present time interval.
The microgrid control method handles planned outages. The "second control objective," used to determine generator power set points, incorporates a load shedding variable that accounts for planned outages. This minimizes load shedding during the present time interval. The resource schedule is generated using the "first control objective" and is based on renewable generation and load forecasts.
11. A microgrid energy management system for controlling operation of a microgrid which comprises a plurality of distributed energy resources including controllable distributed electric generators and electrical energy storage devices, the microgrid energy management system comprising a processing circuit operable to: periodically update a distributed energy resource schedule for the microgrid that includes on/off status of the controllable distributed electric generators and charging/discharging status and rate of the electrical energy storage devices and which satisfies a first control objective for a defined time window, based at least in part on a renewable energy generation and load forecast for the microgrid; periodically determine power set points for the controllable distributed electric generators which satisfy a second control objective for a present time interval within the defined time window, the second control objective being a function of at least the distributed energy resource schedule for the microgrid; periodically updating the distributed energy resource schedule and shifting the defined time window each time the distributed energy resource schedule is updated, wherein the power set points for the controllable distributed electric generators are determined for at least two successive time intervals within the defined time window before the distributed energy resource schedule is updated again and the defined time window is moved, wherein: the first control objective ensures a total power generation capacity of all of the controllable distributed electric generators having an on status as indicated by the distributed energy resource schedule is greater than a critical load of the microgrid for the defined time window; and the first control objective is also a function of a correction factor that accounts for disconnection from power grids or at least one of the controllable distributed electric generators having an on status being out of service during the defined time window so that the total power generation capacity remains greater than the critical load of the microgrid over the defined time window even if the power grids or the at least one controllable distributed electric generator is out of service in an island mode of operation.
A microgrid energy management system uses a processor to manage a microgrid's distributed energy resources (generators, batteries). The processor periodically updates a resource schedule based on renewable energy and load forecasts. This schedule sets generator on/off states and battery charge/discharge rates to meet a "first control objective" over a defined time window. This objective ensures enough power generation capacity exceeds critical load, even with generators offline or the microgrid disconnected. A correction factor accounts for potential generator outages or disconnection from power grids. The processor also periodically determines generator power set points to meet a "second control objective" for the current time interval, considering the resource schedule. Power set points are determined for at least two time intervals before the schedule is updated. The resource schedule and time window are periodically updated.
12. The microgrid energy management system of claim 11 , wherein the first control objective is also a function of an energy storage cost associated with the electrical energy storage devices.
The microgrid energy management system also factors in energy storage costs when updating the resource schedule. The schedule includes on/off status of generators and charging/discharging status/rate of batteries, aiming for a "first control objective" which considers renewable energy and load forecasts. This objective ensures generation capacity exceeds critical load, even with generator outages or disconnection. The energy storage cost is now a component of the first control objective.
13. The microgrid energy management system of claim 12 , wherein the first control objective limits the amount of charging/discharging permitted for the electrical energy storage devices over the defined time window so that the energy storage cost is minimized for the defined time window.
The microgrid energy management system further refines the energy storage aspect. The "first control objective," which considers energy storage cost, limits the charging/discharging of batteries over the defined time window to minimize the energy storage cost during that period. The resource schedule dictates generator on/off states and battery charge/discharge rates. The objective ensures generation capacity exceeds critical load, even with outages or grid disconnection, while minimizing energy storage costs through charging/discharging limits.
14. The microgrid energy management system of claim 11 , wherein the processing circuit is further operable to: update the distributed energy resource schedule each time the renewable energy generation and load forecast is revised.
The microgrid energy management system dynamically adjusts to changing conditions. The resource schedule (generator on/off, battery charge/discharge), initially based on renewable energy and load forecasts, is updated whenever those forecasts are revised. The "first control objective" ensures adequate generation capacity, even with outages or grid disconnection. This ensures the microgrid adapts to real-time forecast changes.
15. The microgrid energy management system of claim 11 , wherein the processing circuit is operable to update the distributed energy resource schedule every hour or less frequently and determine the power set points for the controllable distributed electric generators every fifteen minutes or more frequently.
The microgrid energy management system operates at different frequencies. The resource schedule (generator on/off, battery charge/discharge) is updated hourly or less often. The generator power set points, however, are determined every fifteen minutes or more frequently. The "first control objective" ensures adequate generation capacity, even with outages or grid disconnection. This two-tiered approach balances schedule stability with responsiveness.
16. The microgrid energy management system of claim 11 , wherein the second control objective minimizes an operation cost of the microgrid for the present time interval while minimizing the extent by which the actual charging/discharging rate of the electrical energy storage devices deviates from the charging/discharging rate identified for the electrical energy storage devices in the distributed energy resource schedule.
The microgrid energy management system optimizes operational costs. The "second control objective," used to determine generator power set points, minimizes the microgrid's operating cost for the current time interval. It also minimizes deviations between the actual battery charge/discharge rate and the rate specified in the resource schedule. The "first control objective" is used for the resource schedule, ensuring adequate generation capacity.
17. The microgrid energy management system of claim 11 , wherein the second control objective is also a function of line current and node voltage constraints imposed on the microgrid.
The microgrid energy management system considers grid constraints. The "second control objective," used to determine generator power set points, factors in line current and node voltage constraints imposed on the microgrid. This prevents overloading and voltage instability. The resource schedule is generated using the "first control objective" and is based on renewable generation and load forecasts.
18. The microgrid energy management system of claim 11 , wherein the second control objective is also a function of a weighting factor applied to the charging/discharging rate identified for the electrical energy storage devices in the distributed energy resource schedule.
The microgrid energy management system allows for prioritization of battery usage. The "second control objective," used to determine generator power set points, incorporates a weighting factor applied to the battery charge/discharge rate specified in the resource schedule. This allows the system to prioritize or de-prioritize battery usage based on specific needs or conditions. The resource schedule is generated using the "first control objective" and is based on renewable generation and load forecasts.
19. The microgrid energy management system of claim 11 , wherein the second control objective is also a function of a load shedding variable which accounts for planned outages in the microgrid so that load shedding is minimized over the present time interval.
The microgrid energy management system handles planned outages. The "second control objective," used to determine generator power set points, incorporates a load shedding variable that accounts for planned outages. This minimizes load shedding during the present time interval. The resource schedule is generated using the "first control objective" and is based on renewable generation and load forecasts.
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July 31, 2013
August 15, 2017
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